Tag Archives: sweep net

Southwood writing in 1966 in Ecological Methods, somewhat disparagingly refers to the beating of insects as “This is a collector’s method and originally the tree was hit sharply with a stick and the insects collected in an umbrella held upside down under the stick.” Unfortunately, he committed the cardinal sin of not supplying a supporting reference for his statement – tut, tut! This of course set me off on one of my procrastinatory quests 🙂 Despite the fact that a certain type of beating tray is sold commercially as a Japanese umbrella I was unable to find any mention to the term in the older entomological literature.

Mentions to umbrellas being used to collect insects, yes, and this rather nice colour image with an umbrella shown as an essential part of an entomologist’s equipment (Schaeffer, 1766), also yes; Japanese umbrella, no.

Entomological equipment in the 18th Century from Elementa Entomologia (1766) by Jacob Christian Schaeffer (1718-1790).

It seems that the modern beating tray is descended from two ancestors, the entomological umbrella, which judging by the earliest illustrations must have arisen sometime prior to 1766, and the clap net or clap-net, which was in use by

The entomological umbrella in use (Howard, 1910). Note that the illustration is taken from a work by Ernest August Hellmuth von Kiesenwetter (1820-1880) which I have been unable to track down ☹

British entomologists from at least the same time (Wilkinson, 1978) and which fits in with the usage data from Collins English Dictionary.

Record of usage of the term clap-net (From Collins English Dictionary) Clap nets are used nowadays by ornithologists and bear very little resemblance to the entomological clap net but may explain the couple of more recent peaks in the usage data.

It is likely that the clap net was invented by Benjamin Wilkes possibly in the 1740s (Wilkinson, 1966) as he described how to make one. It is interesting to see that although the clap net was used in a similar way in which we use butterfly nets today, Wilkes points out the need to have a stick with which to beat shrubs and trees to, as he puts it “wherewith to put the flies and moths on the wing”

The clap net in butterfly net mode (Wilkinson, 1966)

Here Newman (1835) highlights the use of the clap net as a beating tray

The clap net (circled) and other entomological equipment, from Ingpen (1849). Note the resemblance to a beating tray.

Ingpen (1849) in his description of the use of the clap net specifically mentions its use as a beating tray “When beating into the net, it will be necessary to keep both sticks in the left hand*, at the same time keeping the head of the net as wide open as possible”. This pretty much how I use my rathe superior(and expensive) beating tray 😊 We then get a mention of the entomological umbrella “In the absence of a clap-net, an open umbrella, will in general be found convenient for beating into; particularly if the inside be lined with white cotton and made to cover the whalebone”. It seems that the umbrella as a beating tray was in common use by the middle of the nineteenth century, for example, “these may be captured by beating the branches over a large net or umbrella” (Douglas & Scott, 1865). This is not to be confused with the beating-net which was an early name for the sweep net (Packard, 1873), the history and use of which I have written about earlier.

So when do beating trays become recognised as beating trays? Banks (1909) refers to both the umbrella, incidentally also using the Keisenwetter illustration, but comments that “A substitute for the umbrella, and in many cases better than it, is the beating cloth. It consists of a piece of common unbleached cot- ton cloth, 1 yard square, to each corner of which a loop of stout twine is sewed, or a corner turned over. Upon reaching the woods, two straight sticks, each about 5 feet in length, and not too heavy, also not so small as to break or bend too easily, are cut from a convenient bush. The sticks are placed crosswise over the cloth and fastened to the loops at the four ends. This is easily and quickly done by making sliding loops of the simple loops. The cloth is thus kept spread out between the sticks. To the center of the sticks another stick may be fastened, so as to hold the cloth out under the branch.” George Day in his 1916 Presidential address to the Entomological Society of British Columbia refers to umbrellas and beating trays in the same sentence “Another method is by beating the foliage of trees and shrubs over a beating tray or inverted umbrella” (Day, 1918). Given that the biologist and novelist, Elliot Grant Watson (1885-1970) refers, somewhat caustically, to beating trays in his essay published in The English Review “Enthusiastic entomologists smashing the young buds from the bushes, holding out beating trays” (Watson, 1923), I am failry confident that the beating tray as we know it, had replaced umbrellas, entomologcial or otherwise, by about 1920. I have still to find out where the term “japanese umbrella” arose. Let me know in the comments if you are able to help.

My modern beating tray – costs about twice as much as the Japanese Umbrella, modern clap net or collapsible beating tray.

Modern beating tray in use – more like the original entomological umbrella depicted by Howard (1910), albeit I am somewhat stouter than the entomologist in his illustration.

Howard, L.O. (1910) The Insect Book. A popular account of the bees, wasps, ants, grasshoppers, flies and other North American insects exclusive of the butterflies, moths and beetles, with full life histories, tables and bibliographies. Doubleday, Page & Company, New York, xxvii + 429 pp.

Ingpen, A. (1849) Manual for the Butterfly Collector or instructions for Collecting, Rearing and Preserving British and Foreign Insects. David Bogue, London.

Watson, E.L.G. (1923) The New Forest, The English Review (September), 318-320

Wilkinson, R.S. (1966) English entomological methods in the seventeenth and eighteenth centuries II: Wilkes and Duffield. Entomologist’s Record and Journal of Variation, 78, 285-292.

Wilkinson, R.S. (1978) The history of the entomological clap-net in Great Britain. Entomologist’s Record and Journal of Variation, 90, 127-132.

*

Were all Victorian entomologists right-handed? I think not 😊. Though that said, even as recently as my mother’s and father’s generation (born in the 1920s) left-handed children were often forced to use their right hands.

I am certain that everyone who has studied biology at university and/or been on a field course, will have used a sweep net and heard the phrase “It’s all in the wrist”. Along with the pitfall trap it is the most commonly used entomological sampling technique used today. Although the premise is simple enough, a sturdy net, attached to a handle that is swept along, through or above low-lying vegetation, when used as a scientific tool and not just as a collecting device, things become somewhat more complex. The sweep net, as an insect collecting device, has been around for at least 180 years, the earliest reference that I have been able to find being Newman* (1835). There are a number of slightly later references in both general entomology texts and group specific books (e.g. Newman, 1844; Clark, 1860; Douglas, 1860; Douglas & Scott, 1865). Instructions for their use at this time are minimal, as this extract from Newman (1841) illustrates.

Newman (1841) a very brief description indeed.

This slightly later description of how to make a sweep net is, however, much more detailed, albeit somewhat sexist.

From Stainton (1852), although he seems to be quoting Newman. Apparently Victorian men were unable to sew.

More detailed, albeit fairly basic instructions on how to use a sweep net can be found in those two invaluable sources, Ecological Methods (Southwood & Henderson 2004) (two pages) and Practical Field Ecology (Wheatear et al., 2011) (one page). I was amused to see that the text in Southwood & Henderson was identical to that of the first edition (Southwood, 1966).

Now we come to the wrist action. There are a surprising number of ways in which you can swing a sweep net, but they all depend on the wrist moving your hand, and hence the net, in a figure of eight. The two most commonly used are what I think of as the one row side step, and the double front step. In the former you walk in a straight line swinging the net backwards and forwards at your side, ideal for sampling a row crop. The latter, the double front step, is similar, but instead of swinging the net at your side, you swing it side to side in front of you as you walk along. In a crop, this is great for sampling multiple rows, in a non-crop a good way of covering a nice wide area of vegetation. There are a further two techniques specifically designed for sweeping the upper part of vegetation, both originally devised for sampling soybean insects, the lazy-8 and the pendulum (Kogan & Pitre, 1980). Both these involve having the net raised, the lazy-8 with the net raised above the crop at the back and front swings, whereas in the pendulum, the net is kept within the crop on the fore and reverse swings. The final bit of wrist action, and arguably the most important and difficult to learn, is the flick-lock, which neatly seals the net and stops your catch escaping.

Having completed your sample of however many sweeps (remember a complete sweep is the figure of eight), and sealed your net, the next step is to transfer your catch to your collecting tubes, bags or jars. A good sweep net, as well as being made from tough material, should be a bit sock shaped. By this I mean that there is a ‘tail’ at the base of the net which helps make your catch more manageable if you are transferring directly to a plastic bag, as you are able to grab the net above the ‘tail’ end and push it into the collecting bag, before everting the net.

When I was a student, the sweep nets we were supplied with, were large enough to stick not just your head inside, but also to get your arms in, so that you could Poot up anything interesting, your shoulders forming the seal to the net. Admittedly you did sometimes have an angry bee or wasp to contend with, but that was a rare event 🙂 Nowadays, sweep nets seem to be constructed on a much more modest scale, which makes sticking your head, let alone your shoulders into one, somewhat difficult.

Even the biggest modern one is too small for me to get my arms in to do some Pooting.

I was pleasantly surprised on an ERASMUS exchange visit to the University of Angers a few years ago, to find that the French, or at least those in Angers, were using sweep nets that were big enough for me to actually delve inside just as I did when I was a student 🙂

The joys of a sweep net with a view 🙂

Despite their undoubted popularity, value for money and relative ease of operation, there are a number of problems associated with sweep netting as a sampling technique. Although these problems are summarised elsewhere (Southwood & Henderson 2004; Wheater et al., 2011) I can’t resist putting my own personal slant on the subject.

The type of habitat can have a marked effect on what you catch. Not all habitats are equally amenable to sweeping; spiny and woody vegetation poses more problems than a nice meadow and you need a really tough net for moorlands 🙂

A sweep net doesn’t necessarily give you an accurate picture of the species composition of the habitat. Not all insects are equally catchable, you are for example, much more likely to catch Hemipterans than you are Coleopterans (e.g. Standen, 2000)

The vertical distribution of the insects also affects what you catch. Many insects have favourite positions on plants e.g. the cereal aphid, Sitobion avenae prefers the ears and leaves, whereas the bird cherry-oat aphid, Rhopalosiphum padi is usually found at the bottom of the plant (Dean, 1974).

The weather; anyone who has tried sweep netting during, or after, a rain storm knows that this is the ultimate act of folly 🙂 Wet nets and wet samples are not a marriage made in heaven.

Time of day can also affect what you are likely to catch, pea aphids for example, are found at different heights on their host plants at different times of day (Schotzko & O’Keeffe, 1989). To be fair, this is of course not just a problem confined to sweep net sampling.

Sweep nets have a fairly well-defined height range at which they work best, they are not good at sampling very short grass and once the vegetation gets over 30 cm you start to miss a lot of the insects associated with it as the net doesn’t reach that far down. Also the efficiency of the sweep netter is reduced.

Finally, how the hell do you standardise your sweeps, not only between sweepers, but as an individual? Additionally, can you reliably use them quantitatively? This has been recognised as a problem for a long time (DeLong, 1932). No one disagrees that sweep netting, provided all the caveats listed above are taken into account, gives a very good qualitative and comparative idea of the arthropod community of the area you are sweeping and they have been so used in many important ecological studies (e.g. Menhinick, 1964; Elton, 1975; Janzen & Pond, 1975) and extensively in agricultural systems (e.g. Free & Williams, 1979; Kogan & Pitre, 1980). Comparing any sampling technique with another is difficult, and any attempt to quantify a catch so that specific units can be assigned to the area or volume sampled is welcome. This has been attempted for the sweep net (Tonkyn, 1980), although I confess that I have never seen anyone use the formula developed by him. In fact, although, according to Google Scholar his paper has been cited thirteen times, only one of the citing authors actually uses the formula, the rest just use him to cite sweep netting as a sampling method. Poor practice indeed.

An illustration of how the various components of the sweep net volume formula is derived (from Tonkyn, 1980).

Sweep nets are, despite the inability to get inside them anymore, great fun to use, extremely good at collecting material for ecology and entomology practicals and of course, a great ecological survey tool when used properly. Google Scholar tells me that there are over 38 000 papers that mention them. That many people can’t possibly be wrong 🙂

References

Clark, H. (1860) Catalogue of the Collection of Halticidae in the British Museum. Physapodes and Oedipodes Part 1. Published by the Trustees, London.

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